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Estimating the Immeasurable: Soil PropertiesDredging Tools for the Future
CEDA Dredging Days5/6 November 2009J. Braaksma, J. Osnabrugge and C. de Keizer
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Contents
• Introduction• Control problem for dredging equipment• Model based adaptive control• Examples
• Overflow loss estimator for hopper dredgers• Trail force estimator• Grain size estimator• Anchor position estimator
• Conclusions
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Introduction
Dredging: relocation of dredged material
Environment part of process
Soil characteristics have large influence on the system behaviour
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Control problem for dredging equipment• Typically we use feedback control for set-point tracking
Process+
-Controller
Set-point Controlaction
Output
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Control problem for dredging equipment• Typically we use feedback control for set-point tracking• Process is characterised by dredge equipment,
environment and their interaction
Process
+
-Controller
Set-point Controlaction
OutputDredge equipment
Environment
Interaction
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Control problem for dredging equipment• Typically we use feedback control for set-point tracking• Process is characterised by dredge equipment,
environment and their interaction• Environment may vary significantly
Process
+
-Controller
Set-point Controlaction
OutputDredge equipment
Environment
Interaction
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Control problem for dredging equipment• Fixed controllers will mostly not work under varying
dredging conditions• Varying process behaviour requires special control
solutions• Adaptive control
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Model-based adaptive control
• Models are available that describe the dredging processes• Use models for predicting soil properties
Model
Measuredsoil properties
Predictedsystem behaviour
Inverse Model
Measuredsystem behaviour
Predictedsoil properties
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Model-based adaptive control
Predictedsoil properties
Process
+
-Controller
Set-point Controlaction
OutputDredge equipment
Environment
Interaction
Inverse modelof process
Adaptationlaw
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Examples
The paper describes the following examples:• Overflow loss estimator• Trail force estimator (for DP/DT and Trail Speed Controller)• Grain size estimator• Anchor position estimator
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Overflow loss estimator for hopper dredgers• Overflow losses reduce dredging production• Reduction is required in sensitive ecosystems, causes
turbidity• Measuring means a technical challenge and requires
expensive equipment• Therefore an estimator is developed that requires only
sensors already available on every modern hopper dredger
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Overflow loss estimator for hopper dredgers
0 20 400
2
4
6
8
Time [min]
Flo
w-r
ate
[m3 /s
]
0 20 401000
1100
1200
1300
1400
1500
1600
Time [min]
Den
sity
[kg/
m3 ]
Qi
Qo
ρi
ρo
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Possible applications for the overflow estimator• Active control to reduce the losses in case of environmental
regulation• Active control to increase the losses in case of agitating
dredging• Warning system to operators for prevention of excess
overflow loss
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Trail force estimator
• Trail force during dredging determined by drag head ground interaction
• Force sensors in pipe hinges are expensive and fragile• Solution estimate force based on differential pressure drag
head and accurate model of the ship dynamics
-200
0
200
400
600
800
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Differential Presure [mbar] Force [kN] Speed [cm/ sec]
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Grain size estimator
• The grain size is an important soil property for the dredging process for both the TSHD and CSD.
• Behaviour of dredge pumps, pipes and hopper (sedimentation speed) are significantly influenced by the grain size
• The estimator has been successfully implemented onboard several CSD for optimizing the discharge process
• Other applications of the estimator are: • Optimizing the loading process of a TSHD • Useful for the development of advanced wear models of
pumps, pipes and valves (e.g. life time prediction)
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Grain size estimator
• Experimental data from the CSD Rubens with a discharge pipeline of 7720 m
• Measured inputs are the discharge pressure, mixture flow and density
• The estimated mean grain diameter (309 µm) nicely converges to the measured value (285 µm) resulting in an relative error of 8.4%
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Anchor position estimator
• Correct positioning of the anchors of a CSD is important for the swing process (unfavorable anchor positions -> lower swing speeds -> lower production)
• The anchor position estimator gives an advise to the operator when to reposition the anchors
• Dragging of the anchors is detected and reported to the operator
• The estimated anchor positions is also used to further improve the automation onboard the CSD (e.g. swing speed controller)
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Anchor position estimator
The anchor position estimator is implemented and in use onboard several CSD
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Conclusions
• Soil properties determine large part of the process behaviour
• Sensors that directly measure soil characteristics are either not available or expensive/fragile
• Solution: use estimation techniques where sensors/measurements are not feasible
Estimating the Immeasurable: Soil PropertiesCEDA Dredging Days: 5/6 November 2009
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Thank you for your attention